This invention relates to sensing devices and systems, and is particularly concerned with sensing devices and systems for use in monitoring the presence or activity of specific chemical analytes.
According to one aspect of the present invention a sensing device for use in monitoring the presence or activity of a specific chemical analyte, comprises an enclosure having a membrane-wall that is semi-permeable to said chemical analyte, macromolecular material contained within the enclosure, said material exhibiting physical change in response to contact with said chemical analyte, a sensor contained within the enclosure to respond to said physical change, and means for transmitting a signal from said sensing device dependent on the response of said sensor.
The sensing device according to the invention is especially applicable for monitoring the presence or level of activity of a specific bio-chemical, drug or other analyte in vivo, within the body of a human or animal patient. In this context the sensing device may be provided for implant subcutaneously or otherwise within the patient so that the particular analyte can be sensed as it permeates the semi-permeable wall of the device.
The said material may be such as to exhibit change in a Theological parameter thereof in response to the analyte. The parameter may be viscosity, and the material, which may be for example a mixture of concanavalin A and ficoll, may be responsive to the presence of glucose to exhibit a change of its viscosity or other parameter. In the context of response to glucose, the sensing device of the invention has particular application for in vivo monitoring of the blood-glucose of diabetic patients.
The means for transmitting a signal from the sensing device of the invention may be contained within said enclosure, and said enclosure may be in the form of a capsule wholly or substantially wholly of semi-permeable membrane. Moreover, the means for transmitting a signal from the sensing device may include means for deriving digital data in accordance with the response of the sensor and for transmitting this from said sensing device.
According to another aspect of the present invention a sensing system for use in monitoring the presence or activity of a specific chemical analyte, comprises a sensing device and interrogating means that is operable for interrogating said sensing device, said sensing device comprising an enclosure having a membrane-wall that is semi-permeable to said chemical analyte, macromolecular material contained within the enclosure, said, material exhibiting physical change in response to contact with said chemical analyte, a sensor contained within the enclosure to respond to said physical change, and means operable in response to interrogation of said sensing means by said interrogating means for transmitting a signal dependent on the response of said sensor, to said interrogating means.
The signal dependent on the response of said sensor may be transmitted to said interrogating means by electromagnetic-wave transmission. Similarly, interrogation of said sensing means may be effected by electromagnetic-wave transmission from said interrogating means. In this latter case, electrical power for the means operable in response to interrogation of said sensing means, may be derived from the electromagnetic-wave interrogating transmission.